In recent years, there has been a demand for an organic electronic device such as an organic electroluminescence device (hereinafter also referred to as “organic EL device”) and an organic solar cell to have a larger scale, a lighter weight, a higher flexibility, etc. In particular, a large-scale organic electronic device is demanded to have a high emission efficiency and/or a high power generation efficiency, and to use a transparent electrode having low electrical resistance.
Conventionally, a transparent electrode that uses an indium-tin composite oxide (SnO2—In2O3: indium-tin oxide: ITO) film (hereinafter also referred to as “ITO transparent electrode”) formed on a transparent substrate using a vacuum deposition or sputtering technique has been widely used because of its beneficial properties, such as high electrical conductivity and high transparency.
However, a structure including an ITO transparent electrode disposed on a transparent resin substrate, such as a flexible polyethylene terephthalate (PET) substrate, has a higher electrical resistance than a structure including an ITO transparent electrode disposed on a glass substrate. This characteristic hinders an ITO transparent electrode from being used in a large-scale organic electronic device.
In an effort to reduce the electrical resistance of transparent electrode, a transparent electrode has been considered in which a patterned metal thin wiring and a planar electrode layer are formed on a substrate using a print or application technique to combine surface current uniformity and high electrical conductivity.
One known method for forming a patterned metal thin wiring is to print a pattern of metal nanoparticle-dispersed liquid containing nanoparticles of a material such as silver, gold, or copper, and then sinter the metal nanoparticles. Such metal nanoparticle-dispersed liquid is often produced using a method that uses no or only a low amount of binder to reduce the electrical resistance of the patterned metal thin wiring during sintering at a low temperature or after sintering. This presents a problem in that the patterned metal thin wiring produced using metal nanoparticle-dispersed liquid has low adhesion to the substrate, and is thus easy to peel off.
Thus, to improve adhesion between the substrate and the patterned metal thin wiring, a method is proposed in which an underlying layer is disposed between the substrate and the patterned metal thin wiring.
For example, Patent Literature 1 discloses a base film for printable electronics including a primer coat layer over at least one surface of a plastic film, and having absorption peaks at near 761 cm−1 and at near 1675 cm−1 in an ATR-IR spectrum of the surface of that primer coat layer due to a chemical structure of C═C (carbon-carbon double bond) to achieve excellent adhesion to a wiring circuit (patterned conductive structure).
Meanwhile, Patent Literature 2 discloses a curable resin composition for screen printing, containing a compound having an isocyanurate skeleton that has excellent adhesion to a metal surface, for use as an insulation film material for protecting patterned wiring on the printed circuit board.